A rational advertiser is willing to bid more for someone is more likely to purchase (i.e., for whom the ad would be "good").

Trying to convince me to buy things isn't always good for me, though. It's good if the thing is useful or I already needed one and just need to know about brands, but a lot of advertising is trying to drive up consumption in more general ways that might cost me money unnecessarily.

Rationality requires an actual estimate of the incrementality of your visit. As someone who has worked in the incrementality estimation function of adtech, for a measurment vendor to the likes of YoutTube, TikTok, Meta, etc., I promise you: the advertisers and the publishers have no fucking clue because the masurement companies, in their competition with one another for the business of these internet titans, juice their estimates to make them more attractive.